A. Field of the Invention
The field of the present invention relates generally to methods of treating agricultural lagoons to improve the quality of the water stored therein and used therefrom. More specifically, this invention relates to methods of utilizing sulfuric acid to treat agricultural lagoons and animal manure handling systems used in confined animal feeding operations.
B. Background
It is well known that the storage and treatment of manure and management of manure in storage lagoons is one of the most difficult, expensive and potentially limiting problems facing the agricultural industry today. This problem is particularly prevalent among that portion of the agricultural industry which pertains to confined animal feeding operations, such as those used for dairy, poultry and swine. Animal excrement, in the form of manure, contains high amounts of nitrates and other chemical constituents such as salts, much of which derives from the animal feed, that make such manure undesirable for contact with fresh water sources, such as rivers and underground aquifers, and difficult to treat or remove once it contaminates fresh water. As a result, manure management is an important task for every confined animal feeding operation and can require a significant amount of resources, including labor, land, equipment and financial resources.
In one increasingly popular method of operation, manure handling in confined animal feeding operations consists of a hydraulic flushing system that flushes the animal manure from the animal holding area to deliver the manure, as a slurry, to a storage area where the water is stored and then utilized for irrigation. A portion of the water from the storage area is utilized for recirculation through the waste handling system. The storage areas for animal waste handling systems are usually lagoons, ponds, pits and similar surface storage areas (collectively, referred to as xe2x80x9clagoonsxe2x80x9d) that are located on or near the agricultural property on which the manure is generated. Manure from the lagoon is also used to irrigate agricultural crops, typically after being mixed with four to five parts of fresh water for every one part of recycled water.
The manure from livestock operations is comprised of the dry feed matter that is fed to livestock and the nutrients associated with that feed matter, including magnesium phosphate and calcium phosphate. This material ends up in the manure handling and treatment system where the high solids and nutrients content causes problems, particularly in the lagoons. The high solids content results in sludge buildup in the lagoon, which takes up space in the lagoon that should be used to store water. The sludge buildup also impacts the ability of the pumps to pump fluid from the lagoon and the solids material can plug equipment utilized in the manure handling system. In addition, if the irrigation water that is taken from the lagoon contains high solids content, then this material can hinder crop seed germination and growth. If not managed properly, the high nutrient content of the lagoon water will overload the land with nutrients, particularly nitrogen, which can contaminate groundwater or surface water resources. Salts in the lagoon water can seal the soil, causing drainage and crop growing problems, including toxicity to plants. Odors and gases produced during the decomposition of the manure and other materials in the lagoon can adversely impact air quality and be a nuisance to neighbors who live downwind. As a result, there is continuing demand for livestock producers and handlers to improve their animal manure management practices to develop best management practices (xe2x80x9cBMPxe2x80x9d) to minimize the impact of their livestock operations on the environment and their neighbors.
To improve the operation and efficiency of the manure handling system, most livestock operators utilize one or more waste treatment methods as part of a manure treatment system, such as manure separators, biological materials, flush water, mechanical excavation and slurry spreading. When they function properly, manure separators utilize screens to separate out a portion of the solid materials from the manure slurry prior to the slurry reaching the lagoon. The solid material separated out by the separator is hauled away for fertilizer and used as bedding for animals in free stall barns. Over time, the separator screens and the piping associated with the flushing system can become plugged with precipitate and waste materials. A common form of the precipitate found in the manure handling systems of confined animal feeding operations is struvite, having a chemical composition made up of oxygen, phosphorus, magnesium, hydrogen and nitrogen. As is well know in confined animal feeding operations, struvite build-up in the piping system and flow lines can severely limit the flow capacity of the lines and the pressure available for use to clean the manure handling system. Typically, the struvite build-up occurs over a period of time in the flush lines. This is dependant upon the diet that is fed to the animals and the quality of the water flowing through the lines.
A number of livestock operators favor a biological solution to the foregoing manure handling problems, requiring the introduction of microbes into the lagoon to facilitate a biological breakdown of the solid and liquid nutrient materials stored in the lagoon. Biological agents are costly and can be sensitive to changing conditions. Under some circumstances, the quality of the lagoon can be improved by the addition of fresh water to change its chemical balance. Typically, even with the various treatment methods, mechanical excavation is periodically required when the capacity of the lagoon is diminished to the point where storage capacity and effective treatment are severely impacted. In addition to the excavation, this method of treatment results in additional expense for disposal of the excavated materials. As an alternative, under the right circumstances the livestock operator can pump out excess manure slurry and spread the slurry on agricultural lands utilizing liquid manure trucks. The spreading of slurry requires consideration of the content of the slurry (i.e., percent of nitrogen), the impact of that content on the crops, the amount of material that can be safely and effectively applied to the agricultural land and soil compaction from the trucks driving on the fields while spreading the slurry.
Even with the availability of the foregoing waste treatment methods, a number of problems still exist. For instance, many confined animal feeding operations, particularly in the dairy industry, utilize concrete alleys or lanes which confine and transport the animal manure, both liquid and solid. These alleys are flushed several times a day with recirculating water from the lagoon. The nutrients in the manure can cause bacteria and/or algae growth to accumulate on the concrete alley walkways and cause an animal to slip and fall, which can result in injury or death for the animal. In addition, the pipes carrying the recirculating fluid to and from the lagoon to flush the concrete lanes can become so clogged with struvite, the precipitate material comprising magnesium phosphate and calcium phosphate, and entrapped manure, that the flush system must be operated over much longer periods of time in order to properly flush the alleys of manure. Various tests and a review of research literature has determined that the struvite precipitate material is adaptable for removal with sulfuric acid.
Sulfuric acid is one of the most commonly used and readily available industrial chemicals in the United States. In the agricultural industry, sulfuric acid has a number of uses. Among these is the use of sulfuric acid on soils in open fields, orchards and vineyards to treat high pH soils and those soils having a high free lime or calcium carbonate content. Soils high in sodium, or sodic soils, are also treated with sulfuric acid. Sulfuric acid is also utilized to treat irrigation wells and various piping systems to remove calcium deposits that are plugging the well perforations or the interior of the pipe, thereby preventing the free flow or movement of water. In some instances, such as when high pH and high bicarbonate waters are used, sulfuric acid is injected into the irrigation system in very controlled rates to buffer high pH irrigation water and improve irrigation system water quality. A major limitation with the use of sulfuric acid is its well known corrosive and hazardous nature, requiring sulfuric acid to be handled with great care by trained individuals wearing personal protective equipment and with specialized equipment to avoid injury to persons and damage to equipment. Because of these characteristics, relatively pure sulfuric acid is not typically used as an agricultural amendment.
The above-described conventional methods of treating agricultural lagoons are somewhat expensive, not entirely successful, limited due to by-product handling and relatively manpower intensive. In addition, these methods do not generally address the problems associated with the buildup of precipitate materials in the flush system pipes, manure separators or algae/bacteria on the concrete alleys. What is needed is an effective method of treating agricultural water storage lagoons in confined animal feeding operations at a lower cost and with minimum by-product production and manpower requirements and which are capable of reducing precipitate buildup in pipes and algae or bacterial buildup on concrete alleys. In other words, what is needed is manure management system to perform preventative maintenance for preventing a lagoon system from developing the foregoing described problems.
The method of treating agricultural lagoons and manure management systems in confined animal feeding operations of the present invention solves the problems identified above. That is to say, the present invention discloses a agricultural lagoon treating method that maintains the lagoon and lagoon water in a more useable condition without requiring excessive costs or manpower and without resulting in additional unwanted by-products that must be separately disposed. The recirculating flush fluid from the lagoon also reduces or eliminates precipitate buildup in pipes and the buildup of algae or bacteria on concrete livestock alleys. As such, the method of the present invention is particularly suited for small or large confined animal feeding operations that have animal manure handling systems.
The preferred embodiment of the present invention utilizes relatively pure (i.e., 93% to 98%) sulfuric acid that is controllably released from a storage tank under pressure into a fluid line transporting recirculation water from the agricultural lagoon to the livestock alleys to maintain the pH of the lagoon fluid at approximately 6.5 to 7.0, slightly acidic to neutral. A sulfuric acid injection pump injects the sulfuric acid into the fluid line through a sulfuric acid pressure line and a fluid injector at a rate necessary to maintain the water in the flush line at the desired pH range. The fluid injector injects the acid at or near the center of the water stream in the fluid line. A backflow prevention device, connected to the injector, prevents water from backing up into the acid pressure line. In the preferred embodiment, the water pH is measured by using a hand-held, portable pH meter to check the water pH at a location downstream of the point where the sulfuric acid is injected into the fluid line. Alternatively, if automated operations are desired, an electronic analyzer/controller can be used to monitor the pH level of the water in the lagoon or the fluid lines to send an electronic command to the pump to pump a pre-set or variable (i.e., depending on the pH reading) amount of sulfuric acid into the fluid line. A timer can also be used to determine when the pump is activated to inject acid into the fluid line. In an alternative embodiment of the present invention, the sulfuric acid is gravity fed or pump fed from the acid storage tank through a valve and hose directly to the lagoon at or near the place where the manure steam enters the lagoon.
If the livestock operator has a manure treating system that has been in use for some time and it is having problems, it may be desirable to pre-treat or xe2x80x9cshockxe2x80x9d the system with sulfuric acid by injecting the acid at the manure entry point into the lagoon to lower the pH to a level lower than what would be necessary for usual maintenance of the system. For instance, if at the time of initiating the acidification process there has been buildup of precipitate material in the fluid lines, solid manure in the lagoon and manure separators and/or bacteria and/or algae growth on the concrete alleys used in the manure handling system, it may be desirable to flush the system with fluid having a pH lower than 6.5 to remove the buildup. Once the pipes, alleys and other components of the system are in a relatively clean condition, then the pH level can be adjusted to be in the desired 6.5 and 7.0 range.
The use of the method of the present invention in confined animal feeding operations may reduce or eliminate the need for the addition of microbes to the lagoon water and the mechanical excavation of the lagoon, thereby reducing operating expenses. The use of sulfuric acid to adjust the pH of the lagoon fluid enhances the breakdown of the manure solids in the lagoon and the efficiency of the manure separator. The manure flowing from the livestock alleys is broken down and placed in suspension, making it easier to transport through pipes and pumps and to use as irrigation water without plugging irrigation valves and other equipment, making it more desirable for re-use. In addition, manure separators will operate more efficiently. In anaerobic conditions and low temperatures, the odors emanating from the lagoon will be increased, primarily from the increased formation of hydrogen sulfide. However, hydrogen sulfide formation can be mitigated by increasing the dissolved oxygen level in the lagoon. This can be accomplished by the introduction of fresh water and/or circulation and aeration of the lagoon.
Accordingly, the primary objective of the present invention is to provide a method of treating agricultural lagoons in confined animal feeding operations that utilizes relatively pure sulfuric acid to clean and prevent precipitate buildup in fluid lines and on the concrete surfaces of the livestock alleys and prevent sludge buildup in the lagoon of an agricultural manure handling system without damaging the pipes, equipment and alleys of that system.
It is also an important objective of the present invention to provide a method of treating agricultural lagoons in confined animal feeding operations that injects relatively pure sulfuric acid into the flush fluid flowing in the fluid line between the lagoon and livestock alleys to flush the alleys and treat the lagoon.
It is also an important objective of the present invention to provide a method of treating agricultural lagoons in confined animal feeding operations that monitors the pH level of the lagoon and injects relatively pure sulfuric acid into the fluid system as needed to maintain the pH of the lagoon at or near 6.5 to 7.0.
It is also an objective of the present invention to provide a method of treating agricultural lagoons in confined animal feeding operations that pumps or flows sulfuric acid into the lagoon from where it is pumped through the fluid line and used to flush the livestock alleys.
It is also an objective of the present invention to provide a method of treating agricultural lagoons in confined animal feeding operations that utilizes sulfuric acid to improve the efficiency of the manure separator and clean the screens used therewith.
It is also an objective of the present invention to provide a method of treating agricultural lagoons in confined animal feeding operations that utilizes sulfuric acid to treat the water and lower the pH to near neutral pH or slightly acidic so the manure slurry can be more readily pumped out of the lagoon and used as part of irrigation water for irrigating agricultural crops.
The above and other objectives of the present invention will be explained in greater detail by reference to the description of the preferred embodiment and the attached figures. As set forth herein, the present invention resides in the novel features of form, construction, mode of operation and combination of processes presently described and understood by the claims.